Our transport study with energy uncoupled ecf mutants of E. coli has indicated strongly that the ECF is intimately involved in the coupling of metabolic energy to active transport of amino acids and certain sugars. Specifically we have shown the ECF is essential for (1) the maintanance of the transmembrane potential, (2) coupling the electrochemical proton gradient (Delta approximately over micron H ion) to the transport process, and (3) controlling the membrane proton and nucleotide permeability. Furthermore, we have identified genetically the ECF as the primary biochemical target of Colicin K. Work is now in progress in identifying the ECF protein that is required for the shock-resistant transport systems, as well as the direct energy donor for the shock-sensitive, binding protein-dependent transport systems.